1Florida State University and 2Boston College

Research has shown that gender differences persist in some areas of science, both in terms of test performance and in the choice of science-related careers. Specifically, while we see a decreasing gender gap in biology and medicine, there is still a substantial under-representation of women in college majors and career choices in the physical sciences, computer science, and engineering (National Science Foundation [NSF], 2013; Snyder & Dillow, 2011). Similarly, gender differences in test scores are often more evident in physical science and engineering, compared to the biological sciences (Martin, Mullis, & Stanco, 2012; NCES, 2012).

There are a number of potential explanations for both the underrepresentation of women in STEM careers and the gender differences in science performance. Among these are differences between men and women in their attitudes and interests in science, as well as differences in particular cognitive skills. One type of cognitive skill – the ability to generate and manipulate mental representations of objects, termed spatial skills –has received particular attention in the context of examining gender differences in science. Spatial skills are related to science performance and show well-documented gender differences (Kozhevnikov, Motes, & Hegarty, 2007; Voyer, Voyer & Bryden, 1995). Yet no study to date has directly examined spatial skills as a potential mediator of gender differences in science performance.

In two studies we focused on spatial skills to help us better understand gender differences in the science test performance of eighth-grade students. Specifically, we asked: Can spatial skills help to explain the gender difference in science test performance?

In Study 1, we administered the Mental Rotation Test, a spatial skills assessment that measures 3D mental rotation ability, to 113 eighth-grade students (13-15 year-olds). This task involves visualizing and rotating 3D images in one’s mind (Vandenberg & Kuse, 1978; see example in Figure 1). We also obtained students’ scores on a state-administered science test (and English/Language Arts test as a covariate). We then investigated how gender differences in mental rotation were related to gender differences in science test scores.

Figure 1. Sample item from the Vandenberg Mental Rotation Test.

We found gender differences on the portions of the test that measured physical science content (such as earth and space science, chemistry, physics) and technology/engineering content. There was no gender difference, however, on the life sciences portion of the test. This pattern parallels the one reported in large-scale studies (Martin et al., 2012; NCES, 2012).

We also found that boys obtained higher scores than girls on the mental rotation assessment, similar to what other researchers have reported (e.g., Voyer et al., 1995). Importantly, we found that after students’ scores on the mental rotation assessment were taken into account, there was no longer a gender difference in physical science scores and the size of the gender difference in technology/engineering scores became substantially smaller. In other words, gender differences in mental rotation skills helped to explain at least a portion of the gender difference in science scores.

In a second analysis, we approached this question from another perspective, by examining gender differences on test items that were more highly correlated with scores on the mental rotation test, compared to items that were less correlated with mental rotation scores. We found that gender differences were larger on test items that were highly correlated with mental rotation scores (see Figure 2).

In Study 2, we further explored the role of spatial skills in the relation between gender and science performance in a larger sample. Specifically, we examined the science test performance of 73,245 eighth-grade students from the entire state of Massachusetts. We used this data to determine whether test items found to be more highly correlated with mental rotation scores in Study 1 were more likely to show gender differences within the Study 2 sample.

First, we found a similar pattern of results for gender differences in science test performance, where there was a larger gender difference in physical science content and technology/engineering content than on the life sciences portion. Most importantly, we found a larger gender difference on test items that were more strongly related to mental rotation test performance than on items that were not as strongly related to mental rotation scores (see Figure 2). This suggests that the relation found with a small group of students in Study 1 might hold with the larger state population.

Figure 2. Gender differences in performance on science test items varying in the degree of correlation with mental rotation score.

One important finding of this research is that boys outperformed girls on some portions of the state science test, which is intended to measure mastery of school-taught content. This gender difference was found in the eighth grade, a time when most boys and girls are exposed to the same science content in the same classrooms. This suggests that perhaps boys have had greater exposure to relevant extracurricular experiences, which increase spatial skills and/or science performance.

Both within our small sample, where we could directly test it, and within the larger sample, where we indirectly tested it, we found that gender differences in spatial skills were indeed useful in explaining gender differences in science test scores. It is critical to consider these findings in the context of research suggesting that spatial skills can be improved through training (Terlecki, Newcombe, & Little, 2008; Uttal et al., 2013) and is therefore a good target for intervention. Taken in this context, our findings suggest that one way that we might be able to improve students’ science performance and diminish the gender difference in science scores is to promote the development of spatial skills. For example, a focus on the teaching of spatial skills in the home and at school, through activities such as building with blocks and doing puzzles, has the potential to train the type of thinking that might facilitate students’ science learning.